/// <summary>
/// Add a new vertex to the field, breaking existing triangles as necessary.
/// </summary>
/// <param name="vtx">Position of the new vertex to add.</param>
private void AddVertexSubdividing(Vector3 vtx)
{
vertices.Add(vtx);
int newVertIdx = vertices.Count - 1;
// Find closest triangle
IndexedBary bary = FindTriangle(vtx);
Debug.Assert(bary.bary.IsInterior, "Should be contained by background seed vertices.");
// Find closest edge
Edge edge = ClosestEdge(bary);
// Find any other triangle with that edge
int oppositieTriIdx = FindTriangleWithEdge(edge, bary.triangle);
bool canSplit = CanSplit(edge, oppositieTriIdx, newVertIdx);
if (canSplit)
{
AddVertexSplitEdge(edge, bary.triangle, oppositieTriIdx, newVertIdx);
}
else
{
AddVertexMidTriangle(bary.triangle, newVertIdx);
}
}
/// <summary>
/// Brute force search to find a triangle that the query position projects onto.
/// </summary>
/// <param name="pos">The query position.</param>
/// <returns>The triangle projected onto, with interpolation information.</returns>
/// <remarks>
/// Note the returned value is never null. Also, if there is any data to query (Add() has been
/// called with a vertex list of length > 0), then the returned value.bary will also be non-null
/// and valid.
/// However, if there is no data to query, then returned_value.bary will be null.
/// </remarks>
private IndexedBary FindTriangle(Vector3 pos)
{
IndexedBary bary = new IndexedBary();
bary.bary = new Interpolant();
for (int i = 0; i < triangles.Count; ++i)
{
Triangle tri = triangles[i];
Vector3 p0 = vertices[tri.idx0];
p0.y = 0;
Vector3 p1 = vertices[tri.idx1];
p1.y = 0;
Vector3 p2 = vertices[tri.idx2];
p2.y = 0;
/// Note area will be negative, because this is xz, not xy, but that will cancel with the negative cross products below.
float area = Vector3.Cross(p2 - p1, p0 - p1).y;
if (area >= 0)
{
area = 0;
}
Debug.Assert(area < 0, "Degenerate triangle in Find");
Vector3 ps = new Vector3(pos.x, 0, pos.z);
bary.bary.weights[0] = Vector3.Cross(p2 - p1, ps - p1).y / area;
bary.bary.weights[1] = Vector3.Cross(p0 - p2, ps - p2).y / area;
bary.bary.weights[2] = Vector3.Cross(p1 - p0, ps - p0).y / area;
if (bary.bary.IsInterior)
{
bary.triangle = i;
bary.bary.idx[0] = tri.idx0;
bary.bary.idx[1] = tri.idx1;
bary.bary.idx[2] = tri.idx2;
return(bary);
}
}
Debug.Assert(false, "Found no triangle for which this position is interior.");
bary.bary = null;
return(bary);
}
/// <summary>
/// Find the edge closest to the interpolation point, or equivalently the edge opposite the
/// vertex with the weakest influence.
/// </summary>
/// <param name="bary">The triangular interpolation.</param>
/// <returns>Edge data for strongest edge.</returns>
private Edge ClosestEdge(IndexedBary bary)
{
Triangle tri = triangles[bary.triangle];
Edge edge;
edge.idx0 = tri.idx1;
edge.idx1 = tri.idx2;
float minWeight = bary.bary.weights[0];
if (bary.bary.weights[1] < minWeight)
{
edge.idx0 = tri.idx0;
edge.idx1 = tri.idx2;
minWeight = bary.bary.weights[1];
}
if (bary.bary.weights[2] < minWeight)
{
edge.idx0 = tri.idx0;
edge.idx1 = tri.idx1;
}
return(edge);
}